1. Field of the Invention
The present invention relates to a printing apparatus for recording images on printing plates mounted peripherally of plate cylinders, feeding processing solutions from processing solution feed rollers to the plates to develop image areas of the plates having the images recorded thereon, and thereafter printing the images by feeding ink to the plates. The invention relates also to a processing device for use in the printing apparatus.
2. Description of the Related Art
In an ordinary conventional printing apparatus, a prepress process is carried out first to make a plate by exposing the plate placed in contact with a film having a binarized black and white image recorded thereon. Then, the plate is loaded into the printing apparatus to carry out a printing process.
Recently, printing apparatus commonly called digital printers have been proposed, one such printer being capable of performing both the prepress process and printing process. The digital printers employ a xe2x80x9ccomputer-to-platexe2x80x9d system for forming images on plates by directly scanning and exposing the plates with laser beams or the like modulated with image signals.
A processing device for use in such a printing apparatus is described, for example, in Japanese Patent Publication (Unexamined) H11-105235 (1999). This processing device places a developer feed roller in contact with a printing plate to feed a developer to an image area thereof, and then places a fixer feed roller in contact with the plate to feed a fixer to the image area, thereby developing and fixing the image area having an image recorded thereon.
In the processing device described in the above publication, processing solutions such as the developer and fixer are fed to the image area of the printing plate from the developer feed roller and fixer feed roller placed in contact with the image area. Thus, the image area is rubbed by the developer feed roller and fixer feed roller. This could result in a processing unevenness due to vibration of the developer feed roller and fixer feed roller.
In the developing process for processing the image area of the plate with the developer, silver is continually deposited around cores provided by silver deposits formed from the developer initially contacting the image area. In the construction where the developer feed roller is placed in contact with the image area to feed the developer to the image area, the silver deposits formed immediately after the developer is fed are rubbed by the developer feed roller. This could result in an imperfect deposition of silver. In such a case, the plate has reduced durability after the developing process.
Further, it is desirable that, in such a printing apparatus, the processing device is easily movable to a position for maintenance services.
An object of the present invention, therefore, is to provide a processing device in a printing apparatus which is free from a processing unevenness due to vibration of a developer feed roller and a fixer feed roller, and which can prevent reduced durability due to an insufficient deposition of silver.
The above object is fulfilled, according to the present invention, by a processing device in a printing apparatus for recording an image on a plate mounted peripherally of a plate cylinder, developing an image area of the plate with the image recorded thereon by feeding a processing solution from a processing solution feed roller to the plate, and printing the image by feeding ink to the plate, wherein the processing device comprises a processing solution tank for storing the processing solution for processing the plate; the processing solution feed roller having a portion thereof immersed in the processing solution stored in the processing solution tank; a drive mechanism for rotating the processing solution feed roller; and a positioning mechanism for positioning the processing solution feed roller such that a surface of the processing solution feed roller is slightly spaced from a surface of the plate; whereby the processing solution feed roller feeds the processing solution to the image area without contacting the image area.
With the above processing device, the processing solution may be applied to the image area of the plate in a noncontact mode. This construction effectively avoids a processing unevenness due to vibration of a developer feed roller or fixer feed roller, and reduced durability due to an insufficient deposition of silver.
In one preferred embodiment, the positioning mechanism includes positioning members having a larger outside diameter than the processing solution feed roller, and mounted coaxially on opposite end portions of the processing solution feed roller.
Preferably, the positioning members are arranged to contact the plate between side edges of the plate and side edges of the image area.
The positioning members may be arranged to contact the plate cylinder in regions thereof outwardly of opposite sides of the plate.
In another preferred embodiment, the drive mechanism is operable to rotate the processing solution feed roller with the surface thereof slightly spaced from the surface of the plate to form an accumulation of the processing solution between the surface of the plate and the surface of the processing solution feed roller before applying the processing solution to and processing the image area of the plate.
Preferably, the drive mechanism is operable to rotate the processing solution feed roller with the surface thereof slightly spaced from the surface of the plate, in a position opposed to a region between a forward end of the plate and a forward end of the image area.
In another aspect of the invention, a printing apparatus is provided, which comprises a plate cylinder for supporting a plate mounted peripherally thereof; an image recorder for recording an image on the plate mounted peripherally of the plate cylinder; a processing device for feeding a processing solution to and processing an image area of the plate where the image is recorded, the processing device including a processing solution feed roller slightly spaced from the image area to feed the processing solution to the image area in a substantially non-contact mode, and a drive mechanism for rotating the processing solution feed roller; an ink feed mechanism for feeding ink to the plate; and a transfer mechanism for transferring the ink from the plate to printing paper.
In a further aspect of the invention, a printing apparatus comprises a plate cylinder for supporting a plate mounted peripherally thereof; an image recorder for recording an image on the plate mounted peripherally of the plate cylinder; a processing device for feeding a processing solution to and processing an image area of the plate where the image is recorded, the processing device including a processing solution feed roller for feeding the processing solution to the image area, and a roller moving mechanism for moving the processing solution feed roller between a processing position adjacent the plate mounted peripherally of the plate cylinder and a retracted position away from the plate; a moving mechanism for moving the processing device in a substantially horizontal direction perpendicular to an axis of the plate cylinder; an ink feed mechanism for feeding ink to the plate; an impression cylinder rotatable with printing paper mounted peripherally thereof; a blanket cylinder for transferring the ink from the plate to the printing paper mounted peripherally of the impression cylinder; a printing paper feed mechanism for feeding the printing paper to the impression cylinder; and a printing paper discharge mechanism for discharging the printing paper having been printed from the impression cylinder.
With these printing apparatus, the processing device may easily be moved to a position for maintenance services.
Other features and advantages of the present invention will be apparent from the following detailed description of the embodiments of the invention.